Brush for dynamo-electric machinery



April 14, 1931. F. H. PRITCHARD BRUSH FOR DYNAMO ELECTRIC MACHINERY Original Filed Oct. 2, 1929 I u. w .h n L m cm n t n A eH .5 Wm H 1m b Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE FRANKLIN H. PRITCHARD, OF ERIE, PENNSYLVANIA, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEXV YORK BRUSH FOR DYNAMO-ELECTRIC MACHINERY Application "filed October 2, 1929, Serial No. 396,774. Renewed December 20, 1930.

14, caused destructive arcing between them.

Also the countersinks have been of such depth that the mechanical strength of the brush adjacent the connection has been greatly reduced.

The object of my invention is to provide an improved fastening means and method for securing the flexible connector to the brush so that it will not be loosened by vibration or repeated heating and cooling and so that destructive arcing between the brush and connector will be avoided.

A further object of my invention is to provide an improved fastening means for securing the flexible connector to the brush which shall not require the brush to be of considerable thickness in order to have suflicient mechanical strength at the point of connection.

'My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention Wlll be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a view, partly in section, of an electrical connection embodying my invention in an initial stage of assembly; Fig. 2 is a view similar to that of Fig. 1 illustrating the permanent connection, and Fig. 3 is a perspective view of the brush and flexible conductor connected thereto.

Referring to Fig. 1, a carbon brush member l is provided with an opening or bore 2 extending therethrough, one end of the bore communicating with a countersink 3 in which is disposed the eyelet 4; of a flexible conductor 5 which is to be electrically and mechanically connected to the brush member. The eyelet 4 is provided with a central opening through which a rivet 6 extends transversely of the brush. The eyelet 4 may be held by the rivet 6 against the brush in any suitable manner and in the present instance the rivet is of tubular form so that it may be upset at its end to form a retaining flange 7 for retaining the eyelet within the countersink.

It has previously been the practice to provide a countersink at the opposite end of the bore in which are placed several washers or equivalent elements so that as the rivet is upset over the washers, they are compressed so as to effect firm conducting engagement between the conductor and the brush. Due to the fact, however, that the countersink in the above described construction is nearly as deep as the countersink within which the conductor eyelet is placed, it will be apparent that the mechanical strength of the brush is considerably lessened where this type of connection is employed and this reduction in the mechanical strength may be so great that the brushes break while in use.

In order to provide means for maintaining the electrical conductor in firm conducting engagement with the brush, while at the same time providing suflicient mechanical strength for the connection, I form a comparatively shallow conical countersink 8 in registry and in communication with the bore 2, and provide a flat or substantially flat washer 9 of resilient material such as steel, for maintaining the proper pressure between the conductor and brush. The final connecting operation comprises inserting the washer 9 within the countersink and on the rivet 6 after which the protruding end of the rivet, as illustrated in Fig. 1, is upset and pressed towards the bottom of the countersink so as to force the washer into conformity with the conical face thereof as illustrated in Fig. 2. The depth of the conical countersink should not be great as it is important that the resilient washer shall not be stressed beyond its elastic limit in order that it may tend to return to its or counterbore. By utilizing a flat resilient washer and pressing it into conical form a greater pressure may be exerted to effect a good connection than 1n the case of a conical washer or the like which has been pressed into a substantially flat shape.

The operation of pressing the resilient washer into its conical shape by upsetting the corresponding end of the rivet may be performed in any suitable manner as by'a swaging operation, and the elements when permanently assembled are, disposed as illustrated in Figs. 2 and 3. V

In order more completely to illustrate my invention, the depth of the countersink has been exaggerated in the drawing and it will be apparent that the countersink need be but of sufiicient depth for the single resilient washer and upset end of the rivet.

Vfhat I claim as new and desire to secure by Letters Patent of the United States is: 1. In combination, a brush having an opening therein, a flexible conduct r, means extending through said opening for securing said conductorto said brush, said opening comprising a. conical countersink on one side of the brush, and resilient means within said conical countersink for pressing and maintaining said conductor into firm engagement with the brush.

.2. In combination, a brush having a bore extending 'therethrough, said bore communicating with a conical countersink on one side of the brush, a flexible conductor, a member extending through said bore for securing said conductor to said brush, and a resilient deformable element seated within said conical countersink coacting with said member for urging said conductor into firm conducting engagement with said brush.

3. In combination, a brush having a bore extending therethrough, said bore communicating with a conical countersink at oneside of the brush, a rivet extending through said bore for securing said conductor to said brush, and a resilient washer seated withinsaid conical countersink, said washer maintained in conformity with'the shape of the countersink by one end of said rivet whereby said conductor is held in firm con-f ducting engagement with said brush;

1 4. In combination, a brush having a'bore extenchng theret-hrough, said bore communicating with a conical countersinkonone'side of the brush, a flexible conductor, a, tubular rivet extending-through said bore for'securing-said conductor to said brush at the opposite side thereof, anda washer of'resilient material seatedwithin said countersink and beneath an upset'portion of said rivet, said rivet holding, the, washer in conformity with the shape of the conical countersink whereby said conductor is malntainedin firm conducting engagement with the brush.

which the rivet extends on one side of the brush, inserting a washer of resilient mate: rial within said countersink and on the cor responding end of said rivet, and upsetting that end of the rivet so as to press said washer into conformity with the conical side of the countersink whereby the aforesaid conductoris held in firm conducting engagement with the brush.

6. In combination, a brush having a bore extending therethro-ugh, said bore communieating with a shallow conical countersink at one side of the brush, a rivet extending through said'bore for securing said conductor to said brush, and a, circumferentially continuous resilient washer seated within said conical countersink, said washer main tained in conformity with the shape of the countersink by one end of said rivet whereby said conductor is held in firm conducting en gagement with said brush. 7

In witness whereof, I have hereunto set my} and this 24th day of September, 1929.

FRANKLIN H. PRITCHARD. 

